1. Field of the Invention
The present invention is directed to valves, and in particular to valves of the delayed-closure variety.
2. Background Information
There are many applications in which it is desired that manual-valve operation result in only a limited amount of flow. One example occurs in public restrooms, where it is desirable not to rely on users to turn faucets off. To achieve this end, faucets are opened by push buttons or similar operators that return automatically to their rest states when they are released and thereby permit their valves to close again. But it would be inconvenient for the water flow to stop as soon as the user releases the actuator, since the user typically wants to wash the hand that be used to press the push button. So the valve is arranged to impose a time delay.
U.S. patent application Ser. No. 09/761,533, which was filed on Jan. 16, 2001, by Parsons et al. for a Flush Controller Having Remote Time-Delay Valve, gives an example of another use for delayed-closure valves. In that arrangement, such a valve is employed to control pressure relief of a pilot chamber whose pressurization causes a toilet""s flush valve to close and whose depressurization allows it to open. The user depresses a push button only momentarily, but the pilot chamber""s pressure must remain relieved long enough to result in an effective flush. The delay imposed by the particular type of valve described in that application depends on the operator travel that caused the valve to open, and that application describes ways of controlling flush volume by making the operator travel adjustable.
In short, there are many applications in which it is desired to supply a predetermined flow volume, and significant effort has therefore been expended to provide effective valve systems for that purpose.
I have found a way of so improving such valves as to increase the accuracy with which they deliver a predetermined flow volume. Specifically, I make the delay duration decrease as the valve""s inlet pressure increases. This reduces the delivered-volume variation that pressure changes can cause.
Specifically, I provide an operator stop that defines the travel limit of the operator by which the user causes the valve to open. The length of that travel largely determines the valve""s closure delay, and I make the stop resiliently expandable so as to vary the travel that the stop permits. In particular, a pressurizer conduit places the valve inlet into communication with an interior chamber that the stop forms, and pressurizing that chamber tends to expand the stop and thereby reduce the operator""s range of travel. This makes the delay relatively low when the pressure is relatively high. It thereby compensates for the higher rate of flow that the higher pressure tends to cause.